The present invention relates to a process for preparing 1,4-diaminonaphthalene and/or 1,5-diaminonaphthalene from naphthalene.
1,4-diisocyanatonaphthalene was mentioned for the first time in the literature as a starting material for polyurethanes in Ann. Chem. 562, 6 (1949). Due to the lack of a cost-effective manufacturing process for 1,4-diaminonaphthalene and hence for 1,4-diisocyanatonapththalene, only a few areas of application for 1,4-diisocyanatonaphthalene are described in the literature. Examples of such areas of application are the preparation of polyurethane-based adhesives or fiber additives, which are disclosed in JP-A2-52096295 and DE-A1-2403656.
An isocyanate component used for the preparation of naphthalene-based polyurethane according to the prior art is mainly 1,5-diisocyanatonaphthalene, which is used in the preparation of polyurethane elastomers.
1,5-diisocyanatonaphthalene is prepared industrially by the phosgenation of the corresponding diamine 1,5-diaminonaphthalene. In accordance with the prior art, 1,5-diaminonaphthalene is prepared via the sulfonation of naphthalene and the subsequent substitution of the sulfonic acid groups with amino groups (DE-C1-3840618).
1,4-diaminonaphthalene, on the other hand, is reacted with 1,4-naphthalene diisocyanate for the synthesis of polyamides, polyimides and polyimines, and also for the preparation of conductive or electro-luminescent polymer materials, as described, for example, in the patent specifications JP-A2-06346050 and JP-A2-07022670.
Preparation of 1,4-diaminonaphthalene in accordance with the prior art is currently limited to preparation by azocoupling starting with 1-naphthylamine (JP-A2-51133237, Rev. Farm. Bioquim. Univ. Sao Paolo (1977), 15 (1-2), 19-25) and via the reaction of hydroxylamine with nitronaphthalene in strongly alkaline medium to form 1-nitro-4-aminonaphthalene (J. prakt. Chem. 156, 315 (1940), Chem. Ber., 22 (1899) 1374). These processes represent multi-stage syntheses with high production costs and low yields in addition to cost-intensive raw materials.
Polyurethanes based on 1,4-diisocyanatonaphthalene and 1,5-diisocyanatonaphthalene possess advantageous properties, so that a practicable synthesis routes for the preparation of 1,4-diaminonaphthalene and 1,5-diaminonaphthalene and their corresponding isocyanates are required.
The object of the present invention is to provide a simple process for the preparation of 1,4-diaminonaphthalene and/or 1,5-diaminonaphthalene.
This and other objects which will be readily apparent to one skilled in the art are accomplished by reacting naphthalene with a halogen and reacting the halogenated naphthalene with ammonia and/or an organic amine, optionally, in the presence of a catalyst.
The present invention relates to a process for preparing 1,4-diaminonaphthalene and/or 1,5-diaminonaphthalene by
a) reacting naphthalene with a halogen,
b) optionally, separating 1,4-dihalogen naphthalene and/or 1,5-dihalogen naphthalene from the mixture from step a),
c) re acting the mixture from step a) or the 1,4-dihalogen naphthalene and/or the 1,5-dihalogen naphthalene from step b) with ammonia and/or an organic amine in the presence of a catalyst.
The selective dihalogenation of naphthalene can take place in the absence of a catalyst or it may be catalyzed but it is preferably catalyzed.
If a catalyst is used, suitable catalysts for the dihalogenation reaction include iodine, tin, elements of Groups 8, 10, 12 and 13 of the Periodic Table (nomenclature to I.U.P.A.C 1985), mineral acid salts and oxides of the elements of Groups 8, 9, 10, 12, 13, 14 and 15 of the Periodic Table (nomenclature to I.U.P.A.C 1985) and mineral acids.
Preferably, iodine, iron, tin, zinc, aluminum, nickel, halides or oxides of iron, nickel, aluminum, antimony, arsenic, tin, zinc, boron or phosphoric acid are used.
Suitable halogens include chlorine, bromine and mixtures thereof.
In principle, any solvent which is able to dissolve naphthalene and is not halogenated to a significant extent under the prevailing conditions may be used in the process of the present invention. Dichloromethane, trichloromethane, tribromomethane, tetrachloromethane, tetrabromo-methane, chlorobenzene, dichlorobenzenes and trichlorobenzenes are preferred. Most preferred is trichloromethane.
The procedure adopted for the dihalogenation is preferably such that the halogen, preferably bromine, is introduced into a mixture of naphthalene, solvent and catalyst at an absolute pressure in the range of from about 0.5 to about 10 bar, preferably from 1 bar to 2 bar, most preferably from 1 bar to 1.2 bar, and at a temperature in the range of from 0xc2x0 C. to 150xc2x0 C., preferably from 10xc2x0 C. to 70xc2x0 C., most preferably from 20 to 30xc2x0 C. The naphthalene concentration during the halogenation is preferably in the range of from 5 to 70 wt %, most preferably from 25 to 50 wt %, based on the weight of the solvent.
During the dihalogenation, a mixture containing 1,4-dihalogen naphthalene and 1,5-dihalogen naphthalene is obtained. Prior to amination, the mixture may be purified. The 1,4-dihalogen naphthalene and/or the 1,5-dihalogen naphthalene can also, however, be separated out of the mixture. The 1,4-dihalogen naphthalene or the 1,5-dihalogen naphthalene can be aminated free from isomers in this way.
The separation of the 1,4-dihalogen naphthalene and/or the 1,5-dihalogen naphthalene out of the mixture can be accomplished by taking advantage of the large melting point difference of these isomers, for example, by crystallization.
The halogen-amine substitution is performed in the presence of a catalyst. Suitable catalysts include any of the metals of Groups 8, 9, 10 and 11 of the Periodic Table (nomenclature to I.U.P.A.C 1985) and oxides, acetates and mineral acid salts of metals of Groups 8, 9, 10 and 11 of the Periodic Table (nomenclature to I.U.P.A.C 1985).
The metal catalyst can be in the form of granules, chips, powder or fixed to a support, for example on aluminum oxide, silicon oxide or titanium oxide, or in any other solid form. The chlorides, acetates and oxides can be used, for example, in the form of pellets or as powder or fixed to a support such as aluminum, silicon or titanium oxide.
Preferably nickel, copper, cobalt or iron metal, halides of iron, nickel, copper, cobalt, oxides of iron, nickel, copper, cobalt, acetates of iron, nickel, copper, cobalt are used.
In principle, any solvent which is able to dissolve dihalogen naphthalene and is inert under the prevailing conditions may be used in the process of the present invention. Preferably, water, methanol, ethanol, N,N-dimethyl acetamide, n-propanol, n-butanol, acetonitrile, benzonitrile, dioxan or dioxan/water mixtures or inert solvents which are immiscible with water such as toluene, xylene or aliphatic or cycloaliphatic hydrocarbons of the C6-C12 fraction are used. The use of liquid ammonia as a reaction medium without further solvent addition is also suitable for the amination reaction of the dihalogen naphthalene.
Ammonia as well as any primary and/or secondary amines such as monoalkyl amines, monoacyl amines or dialkyl amines are suitable as amination agents. Ammonia is preferably used.
The yield of the halogen-amine substitution reaction in terms of diamino-naphthalene can be raised considerably if the hydrohalic acid formed, during the reaction is neutralized with a base. Suitable bases include carbonates and hydroxides of Groups 1 and 2 of the Periodic Table (nomenclature to I.U.P.A.C. 1985). Preferably, sodium, potassium, calcium or magnesium carbonate or hydrogencarbonate or sodium, potassium, calcium or magnesium hydroxide or mixtures or mixed crystals thereof are used. The addition of cesium, rubidium or barium chloride, cesium, rubidium or barium sulfate improves the yield-increasing effect of the base. Cesium chloride or cesium sulfate is preferably used.
The halogen-amine substitution is carried out at temperatures in the range of from 0xc2x0 C. to 200xc2x0 C., preferably from 100 to 180xc2x0 C., most preferably from 120 to 160xc2x0 C. and at a pressure of from 1 to 200 bar, preferably from 10 to 150 bar, most preferably from 20 to 120 bar. The concentration of 1,4- and 1,5-dihalogen naphthalene is preferably in the range of from 5 to 70 wt %, most preferably from 30 to 50 wt %, based on the weight of solvent or ammonia in the case of a solvent-free reaction.
After the amination, a purification step or separation step can be carried out and the desired product removed from the reaction mixture. Suitable separation methods include distillation and crystallization.
The proportion of 1,5-dihalogen naphthalene in the mixture of 1,4-dihalogen naphthalene and 1,5-dihalogen naphthalene is generally in the range of from 1 to 50 wt %, preferably from 5 to 40 wt %, most preferably from 10 to 30 wt %. The isomer ratio is determined by the halogenation as a function of the choice of catalyst and the reaction temperature and remains substantially unaltered during the subsequent amination.
The invention also provides a process for preparing mixtures containing 1,4-diisocyanatonaphthalene and 1,5-diisocyanatonaphthalene by
a) reacting naphthalene with a halogen,
b) reacting the mixture from step a) with ammonia in the presence of a catalyst, and
c) phosgenating the mixture from step b).
The present invention also provides a process for preparing 1,4-diisocyanatonaphthalene by
a) reacting naphthalene with a halogen,
b) reacting the 1,4-dihalogen naphthalene from step a) with ammonia in the presence of a catalyst, and
c) phosgenating the 1,4-diaminonaphthalene from step b), in which the 1,5 isomer is separated from the isomer mixture after one of steps a), b) or c).
The invention also provides a process for preparing 1,5-diisocyanatonaphthalene by
a) reacting naphthalene with a halogen,
b) reacting the 1,5-dihalogen naphthalene from step a) with ammonia in the presence of a catalyst, and
c) phosgenating the 1,5-diaminonaphthalene from step b), in which the 1,4 isomer is separated from the isomer mixture after one of steps a), b) or c).
The amines prepared by the process according to the invention can then be phosgenated by any of the known methods to produce the corresponding isocyanate. The resultant isocyanates may be used to produce polyurethanes (e.g. JP-A2-50012062). After phosgenation, a purification step or separation step can be carried out and the desired product, preferably 1,4-diisocyanatonaphthalene, may be removed from the reaction mixture. Suitable separation techniques include distillation and crystallization.
The optionally desired separation of the 1,4 isomer and the 1,5 isomer can also take place after the dihalogenation and/or after the halogen-amine substitution and/or after the phosgenation.